- Issue 1870: Implemented export of expressions that use the initial concentrations / volumes / values to SBML. For this new global parameters as well as initial assignments so that the dependency chain remains. Only the new global parameter has to be changed to affect the expressions and original model entities.
- compile the model also when exporting to string (so far this was only done when exporting to file)
- display error messages when the model cannot be exported rather than failing silently
- add warning when event assignment target already has an assignment rule, or is not present in th
- removed warning
- further improved exporting of initial assignments
- return an empty string instead of false (note: return value not used since an exception is thrown by CCopasiMessage)
- remove unnecessary assert, since the case is handled
- fix warning
- modify Cmake files to install all files necessary that are needed to execute COPASI (this also includes Qt dependencies, examples and wizard files) and command line tools.
- add a variable for the library dir, so it can be overwritten on linux x64 systems (this is used by the perl / python  bindings to install into the proper locations)
- Correct Python install directories
-  Linux / Win: instead of assuming that copasi shared files are located in /share (when not configured),
  change default search location to the share folder next to the current bin folder, as will be the case
  when we distribute files.
- found proper default location for qt library files
- on OSX we need to first fix the app bundle and then install it
- flatten comp models during import
fix typo in comment
rename a method

rename getErrorMean -> getErrorSum and adapt the comments.
The old name was misleading (and I do not think anybody used this call
in third-party software)
Fixed problem caused by invalid event targets.